Techniques to copy an operating system

ABSTRACT

Techniques are described that can be used to enable a transfer of an operating system from one machine to another. The transfer permits the operating system to be available to the target machine at buffers that are accessible to one or more application or other logic. In some implementations, information related to an operating system migration is stored in a buffer that is accessible to an application that is to use the information and thereby avoids a copy of such information from an intermediate buffer to an application buffer.

FIELD

The subject matter disclosed herein relates to techniques to copy anoperating system from one machine to another machine.

RELATED ART

Virtualization is a well-known technique to share hardware resourcesbetween several operating systems. Each operating system “believes” thatit has complete control over its hardware environment and is not awarethat the hardware environment is shared. Virtualization has thecapability to move an operating system (OS) from one physical computernode to another node without the operating system being aware and withminimal interruption of the operating system. This operation is known asVirtual Machine (VM) migration. Examples of applications that performvirtual OS migration include VM Relocation from XenSource Inc. andVMotion and LiveMotion from VMware Inc. It is desirable to completeoperating system migration in a minimum amount of time so that interruptto the operating system is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, in the drawings and in which likereference numerals refer to similar elements.

FIG. 1 depicts an example system embodiment in accordance with someembodiments of the present invention.

FIG. 2 depicts an example of interactive elements in accordance withsome embodiments of the present invention.

FIGS. 3 and 4 depict example flow diagrams that can be used in operatingsystem migration in accordance with some embodiments of the presentinvention.

DETAILED DESCRIPTION

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrase “in one embodiment” or “an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in one or moreembodiments.

Some embodiments provide techniques to use TCP/IP compliant networkprotocol units for migrating an operating system from one machine toanother machine. In some embodiments, information related to anoperating system migration is stored in a buffer at a recipient computerthat is accessible to an application that is to use the information.Thereby, copying such information from an intermediate buffer to anapplication buffer may be avoided.

FIG. 1 depicts in computer system 100 a suitable system in which someembodiments of the present invention may be used. Computer system 100may include host system 102, bus 116, and network component 118.

Host system 102 may include chipset 105, processor 110, host memory 112,and storage 114. Chipset 105 may provide intercommunication amongprocessor 110, host memory 112, storage 114, bus 116, as well as agraphics adapter that can be used for transmission of graphics andinformation for display on a display device (both not depicted). Forexample, chipset 105 may include a storage adapter (not depicted)capable of providing intercommunication with storage 114. For example,the storage adapter may be capable of communicating with storage 114 inconformance at least with any of the following protocols: Small ComputerSystems Interface (SCSI), Fibre Channel (FC), and/or Serial AdvancedTechnology Attachment (S-ATA).

In some embodiments, chipset 105 may include data mover logic (notdepicted) capable to perform transfers of information within host system102 or between host system 102 and network component 118. As usedherein, a “data mover” refers to a module for moving data from a sourceto a destination without using the core processing module of a hostprocessor, such as processor 110, or otherwise does not use cycles of aprocessor to perform data copy or move operations. By using the datamover for transfer of data, the processor may be freed from the overheadof performing data movements, which may result in the host processorrunning at much slower speeds. A data mover may include, for example, adirect memory access (DMA) engine. In some embodiments, data mover maybe implemented as part of processor 110, although other components ofcomputer system 100 may include the data mover. In some embodiments,data mover may be implemented as part of chipset 105.

Processor 110 may be implemented as Complex Instruction Set Computer(CISC) or Reduced Instruction Set Computer (RISC) processors,multi-core, or any other microprocessor or central processing unit. Hostmemory 112 may be implemented as a volatile memory device such as butnot limited to a Random Access Memory (RAM), Dynamic Random AccessMemory (DRAM), or Static RAM (SRAM). Storage 114 may be implemented as anon-volatile storage device such as but not limited to a magnetic diskdrive, optical disk drive, tape drive, an internal storage device, anattached storage device, flash memory, battery backed-up synchronousDRAM (SDRAM), and/or a network accessible storage device.

Bus 116 may provide intercommunication among at least host system 102and network component 118 as well as other peripheral devices (notdepicted). Bus 116 may support serial or parallel communications. Bus116 may support node-to-node or node-to-multi-node communications. Bus116 may at least be compatible with Peripheral Component Interconnect(PCI) described for example at Peripheral Component Interconnect (PCI)Local Bus Specification, Revision 3.0, Feb. 2, 2004 available from thePCI Special Interest Group, Portland, Oreg., U.S.A. (as well asrevisions thereof); PCI Express described in The PCI Express BaseSpecification of the PCI Special Interest Group, Revision 1.0a (as wellas revisions thereof); PCI-x described in the PCI-X Specification Rev.1.1, Mar. 28, 2005, available from the aforesaid PCI Special InterestGroup, Portland, Oreg., U.S.A. (as well as revisions thereof); and/orUniversal Serial Bus (USB) (and related standards) as well as otherinterconnection standards.

Network component 118 may be capable of providing intercommunicationbetween host system 102 and network 120 in compliance at least with anyapplicable protocols. Network component 118 may intercommunicate withhost system 102 using bus 116. In one embodiment, network component 118may be integrated into chipset 105. “Network component” may include anycombination of digital and/or analog hardware and/or software on an I/O(input/output) subsystem that may process one or more packets to betransmitted and/or received over a network. In one embodiment, the I/Osubsystem may include, for example, a network component card (NIC), andnetwork component may include, for example, a MAC (media access control)layer of the Data Link Layer as defined in the Open SystemInterconnection (OSI) model for networking protocols. The OSI model isdefined by the International Organization for Standardization (ISO)located at 1 rue de Varembé, Case postale 56 CH-1211 Geneva 20,Switzerland.

Network 120 may be any network such as the Internet, an intranet, alocal area network (LAN), storage area network (SAN), a wide areanetwork (WAN), or wireless network. Network 120 may exchange trafficwith network component 118 using the Ethernet standard (described inIEEE 802.3 and related standards) or any communications standard. Asused herein, a “network protocol unit” may include any packet or frameor other format of information with a header and payload portions formedin accordance with any protocol specification.

Some embodiments provide operating system migration (OM) from anothermachine to host system 102. The another machine may transfer a copy ofan operating system to host system 102 using network protocol unitscompliant with the TCP/IP protocol, although any other protocol may beused. In some embodiments, information related to an operating systemmigration is stored in a buffer in host memory 112 that is accessible toan application that is to use the information and thereby avoids a copyof such information from an intermediate buffer to an applicationbuffer.

FIG. 2 depicts an example of elements that can be used in someembodiments of the present invention in the course of migration of anoperating system from one computer to another. For example, aninformation technology manager may request that a virtual operatingsystem migration occur so that host 201 may use the operating systemexecuted by another computer. For example, the manager may request thevirtual operating system migration in order to perform load balancingamong computers or to continue use of an operating system prior to shutdown of another computer that runs the operating system. The manager mayrequest that the transmitter computer initiate a virtual operatingsystem migration to host 201. In some embodiments, host 201 may includeat least OS migration monitor (OMM) logic 202, stack logic 204, driverlogic 206, regular buffer 208, OM buffer 210, and header buffer 212.Host 201 may include other logic (not depicted) such as but not limitedto a processor, memory device, and storage device.

OMM logic 202 may be capable of managing copying of an image of anoperating system (OS) or other information relating to a migration of anOS from another computer to host 201. OMM logic 202 may in part use avirtual OS migration capability inside a Virtual Machine Monitor (VMM)layer of an operating system executed by host 201. For example, atransmit VMM logic (or other logic) used by another computer maycommunicate with OMM logic 202 to open a TCP/IP socket used to copy theoperating system image to host 201. The socket may be a 4 tuple thatincludes an IP source address, IP destination address, TCP port receive,and TCP transmit port, although other types of information may be usedto identify network protocol units involved in an operating systemmigration. OMM logic 202 may assign OM buffer 210 and header buffer 212for network protocol units that include information related to migrationof a guest OS to host 201. OMM logic 202 may provide the socket todriver 206 to indicate that network protocol units within the socket areto be stored in OM buffer 210 and header buffer 212.

OMM logic 202 may provide to driver logic 206 a descriptor for each OMbuffer. Each descriptor describes a target buffer location and anexpected TCP sequence number for a network protocol unit to be stored inan OM buffer. The expected TCP sequence number may be determined by thedriver from an initial sequence number. OM buffers can be used to storepayloads of received network protocol units. OMM logic 202 (or otherlogic) may identify regular buffers at least to store headers and/orpayloads of traffic that does not carry information relating to an OM orthat are within the OM socket but do not have an expected sequencenumber.

Driver logic 206 may be a driver for network component 250. Driver logic206 may be capable to initialize network component 250 and permit otherlogic to interface with network component 250. Driver logic 206 mayassign a ring of one or more descriptor dedicated to the OM socket. Thering may be stored in host memory. Pointers to the start and end of thering may be provided to network component 250. Network protocol unitswithin the OM socket are to be stored in buffers specified in the ring.For example, assigning a ring may include defining a base and size ofthe ring as well as tail and header pointers. A single ring may be usedto point to buffers to store headers and payloads of received networkprotocol units. Other rings may be used to specify buffer locations forother types of received network protocol units. For example, a ring maybe assigned to convey destination buffers for network protocol units notinvolved in an OM or network protocol units that are involved in an OMbut do not have an expected sequence number.

Driver logic 206 may identify OM buffers to network component 250 usingthe ring dedicated to the OM. For example, the network component maystart using the buffers specified in the ring for the OM to storereceived network protocol units when the tail pointer value is increasedso that the header pointer value does not match tail pointer value.Target buffers may be provided to network component 250 until the OMsocket is closed. For example, closing the OM socket may be achievedwhen a network protocol unit in the OM socket indicates the OM socket isto be closed such as by indication of “FIN” using the TCP protocol.

For example, an interrupt may indicate receipt of one or more networkprotocol unit that carries information pertinent to an OM. The networkprotocol unit that carries information pertinent to an OM may becompliant, for example, at least with the TCP/IP protocol. Uponreception of such an interrupt, driver logic 206 may check if thepayload was placed in an OM buffer or a regular buffer. Driver logic 206may indicate receipt of one or more header from one or more networkprotocol unit to stack 204.

Stack logic 204 may perform protocol processing at least of headers ofreceived network protocol units in compliance with the TCP/IP protocol.For example, the TCP/IP protocol is described at least in thepublication entitled “Transmission Control Protocol: DARPA InternetProgram Protocol Specification,” prepared for the Defense AdvancedProjects Research Agency (RFC 793, published September 1981) as well asrevisions thereof. After stack logic 204 processes a header and theheader is approved, stack logic 204 may inform OMM logic 202 that thepayload associated with the approved header is stored in the OM bufferand is available for use.

Host memory of host 201 may include regular buffer 208, OM buffer 210,and header buffer 212. Regular buffer 208 may store network protocolunits not involved in an OM or network protocol units that are involvedin an OM but do not have an expected sequence number. Other types ofnetwork protocol units may be stored in regular buffer 208.

OM buffer 210 may store payloads of network protocol units involved inan OM to host 201 that have an expected sequence number. Networkcomponent 250 may store payloads of received network protocol units intoOM buffer 210. Although not a necessary feature of any embodiment, useof OM buffer 210 may avoid a sequence of copying a payload to a regularbuffer and subsequently copying the payload to an application buffer. OMbuffer 210 may be directly accessible by an application or other logicthat is to use the migrated operating system.

Header buffer 212 may store headers of received network protocol unitsstored into OM buffer 210. Network component 250 may store such headersinto header buffer 212.

In some embodiments, network component 250 may include a transceiverlogic 252, filter logic 254, buffer 256, and data mover 258. Transceiverlogic 252 may be capable to receive network protocol units through aphysical medium and transmit network protocol units through a physicalmedium. The physical medium may be a coaxial cable, wire-line, fiberoptic cable, or other signal propagation medium. Alternatively or inaddition, transceiver logic 252 may be capable to receive and transmitsignals using wireless techniques. For example, transceiver logic 252may receive and transmit network protocol units in conformance withapplicable protocols such as Ethernet as described in IEEE Standard802.3 (2002) and revisions thereof, although other protocols may beused. Transceiver logic 252 may be used to perform media access controloperations as prescribed by applicable protocols such as Ethernet,although other protocols may be used, as well as other protocol-relatedprocessing.

Filter logic 254 may determine whether a received network protocol unitcarries information relevant to an OM to host 201. Various techniquescan be used to determine whether the received network protocol unitcarries information relevant to an OM. For example, network protocolunits relevant to an OM may be identified by having 4-tuples that matchthe socket for the OM. For example, host 201 may identify one or moresocket of network protocol units that carry information relevant to anOM. Each network protocol unit relevant to an OM may be directed to bestored in an OM buffer identified in the descriptor ring associated withthe OM socket provided that the network protocol unit has a sequencenumber associated with the OM buffer. Network protocol units notinvolved in an OM or network protocol units that are involved in an OMbut do not have an expected sequence number may be stored in regularbuffer 208.

Buffer 256 may store received network protocol units prior to transferto host 201. Data mover logic 258 may transfer at least network protocolunits for storage in host 201. Data mover logic 258 may store payloadsof received network protocol units into appropriate buffers in hostmemory. For example, a payload of a network protocol unit that carriesinformation relevant to an OM and which has an expected sequence numberis stored to an OM buffer associated with the expected sequence number.

In response to reception of a network protocol unit matching the socketand having an expected sequence number, the payload of the networkprotocol unit may be stored into the OM buffer associated with thesequence number of such network protocol unit and the expected sequencenumber may be increased by the payload size of such network protocolunit. In some embodiments, the sequence number is not increased until asegment having the expected sequence number is received.

The headers of network protocol units that carry information relevant toan OM may be stored in header buffer 212. The location of the headerbuffer may be specified in the descriptor ring.

If the received network protocol unit is not associated with an OM, thereceived network protocol unit may be stored into a regular buffer. Ifthe received network protocol unit does not have an expected sequencenumber, even though it is in the socket associated with the OM, thereceived network protocol unit may be stored into a regular buffer. Forexample, in some cases, TCP/IP segments may be received by a networkcomponent out of order. An out-of-order TCP/IP segment may have asequence number that is unexpected. Each out-of-order TCP/IP segment maybe stored in a regular buffer. However, in some embodiments, anout-of-order TCP/IP segment may be stored in OM buffer 210 and headerbuffer 212. An indication (such as but not limited to an interrupt) maybe provided to the driver that a network protocol unit was stored into abuffer in host memory.

FIG. 3 depicts an example flow diagram that can be used to enablereceipt of network protocol units relevant to an OM in accordance withsome embodiments of the present invention. In block 302, a targetcomputer and a transmitter may establish a TCP/IP socket over which anOM may take place to copy an operating system image to the targetmachine. The socket may be a 4-tuple that includes an IP source address,IP destination address, TCP port receive, and TCP transmit port,although other types of sockets may be used.

In block 304, logic responsible for managing an OM may indicate to thedriver a socket for the OM. The driver may be associated with a networkcomponent capable to receive network protocol units.

In block 306, logic responsible for managing an OM may assign one ormore buffer for the network protocol units involved in the OM. In someembodiments, each network protocol unit in the OM has an allocatedbuffer for the payload and a separate allocated buffer for the header.In some embodiments, TCP/IP compliant network protocol units are used toperform the OM. The logic responsible for managing the OM may provide todriver logic descriptors for each assigned buffer. Each descriptor maydescribe a target buffer location and an expected TCP sequence numberfor a network protocol unit to be stored in the buffer. Sequence numbersof the buffers may be expected to be contiguous. The logic responsiblefor managing an OM may identify regular buffers to store headers and/orpayloads of traffic not used in an OM. Driver logic may provide thebuffers to network component using the ring dedicated to the OM. Targetbuffers may be provided to the network component until the socket forthe OM is closed. As long as the OM socket is open, the logicresponsible for managing the OM may continue to assign buffers andassociated sequence numbers to network protocol units in the OM and thedriver transfer buffer assignments to the network component.

In block 308, in response to indication of receipt of a network protocolunit, a determination may be made whether a network protocol unit wasplaced in an OM-related buffer or regular buffer. The indication may bein the form of an interrupt to driver logic. The indication may beprovided from a network component logic prior to, after, or atapproximately the same time as a network protocol unit received from anetwork is stored into a buffer in host memory. Network protocol unitsthat carry information related to an OM may be stored in OM-relatedbuffers. A network protocol unit that does not carry information relatedto an OM or has a sequence number other than that expected by thenetwork component may be stored in other buffers. Block 310 may followblock 308 in order to process one or more network protocol unit storedin an OM-related buffer. Block 350 may follow block 308 in order toprocess one or more network protocol unit stored in a regular buffer.

In block 310, a header of a received network protocol unit that carriesinformation related to the OM may be made available to a stack logic.The header may be stored in a dedicated header buffer.

In block 312, the stack logic may process at least one header. After thestack logic processes a header and the header passes inspection, thestack logic may inform OMM logic that the payload associated with theapproved header is stored in the OM buffer and is available to OMMlogic.

In block 350, processing may take place on network protocol units storedin regular buffers. Relevant protocol processing may take place.

FIG. 4 depicts an example flow diagram in accordance with someembodiments of the present invention that can be used in connection withan OM. In block 402, the network component may receive a queue assignedto an OM. The queue may be a descriptor ring where each descriptordescribes a buffer in which to store a header and payload of networkprotocol units involved in an OM as well as a sequence number associatedwith each buffer.

In block 404, the network component may receive an indication that oneor more buffer is available to store received network protocol unitsinvolved in an OM.

In block 406, the network component may determine whether a receivednetwork protocol unit is related to an OM and has an expected sequencenumber. In some embodiments, TCP/IP compliant network protocol units areused to perform the OM. For example, the determination of whether areceived network protocol unit is within an OM may be made based onwhether a socket of the received network protocol unit matches the OMsocket. A sequence number is associated with each buffer. If thereceived network protocol unit is related to an OM and has an expectedsequence number, block 408 may follow. If the received network protocolunit is not related to an OM or does not have an expected sequencenumber, block 450 may follow.

In block 408, the network component may store the network protocol unitin the OM-related buffer in host memory for the sequence number. Theexpected sequence number may be the sequence number of an available OMbuffer that is to be used next and identified by the descriptor ring.The expected sequence number of the next received network protocol unitmay be increased by the payload size of the most recently receivednetwork protocol unit. Increasing the sequence number may be performedin order to verify the network protocol units are in order.

In block 410, the header of the received network protocol unit may bestored into a header buffer associated with the OM. In addition, theheader buffer may be assigned to a particular sequence number.

In block 412, the network component may provide an indication to thedriver that a network protocol unit was stored in the host memory at aparticular buffer.

In block 450, the network component may store the received networkprotocol unit in a regular buffer in host memory. The received networkprotocol unit may be a network protocol unit that do not carryinformation related to an OM and/or has an unexpected sequence number.Block 412 may follow block 450.

Embodiments of the present invention may be implemented as any or acombination of: one or more microchips or integrated circuitsinterconnected using a motherboard, hardwired logic, software stored bya memory device and executed by a microprocessor, firmware, anapplication specific integrated circuit (ASIC), and/or a fieldprogrammable gate array (FPGA). The term “logic” may include, by way ofexample, software or hardware and/or combinations of software andhardware.

Embodiments of the present invention may be provided, for example, as acomputer program product which may include one or more machine-readablemedia having stored thereon machine-executable instructions that, whenexecuted by one or more machines such as a computer, network ofcomputers, or other electronic devices, may result in the one or moremachines carrying out operations in accordance with embodiments of thepresent invention. A machine-readable medium may include, but is notlimited to, floppy diskettes, optical disks, CD-ROMs (Compact Disc-ReadOnly Memories), and magneto-optical disks, ROMs (Read Only Memories),RAMs (Random Access Memories), EPROMs (Erasable Programmable Read OnlyMemories), EEPROMs (Electrically Erasable Programmable Read OnlyMemories), magnetic or optical cards, flash memory, or other type ofmedia/machine-readable medium suitable for storing machine-executableinstructions.

Moreover, embodiments of the present invention may also be downloaded asa computer program product, wherein the program may be transferred froma remote computer (e.g., a server) to a requesting computer (e.g., aclient) by way of one or more data signals embodied in and/or modulatedby a carrier wave or other propagation medium via a communication link(e.g., a modem and/or network connection). Accordingly, as used herein,a machine-readable medium may, but is not required to, comprise such acarrier wave.

The drawings and the forgoing description gave examples of the presentinvention. Although depicted as a number of disparate functional items,those skilled in the art will appreciate that one or more of suchelements may well be combined into single functional elements.Alternatively, certain elements may be split into multiple functionalelements. Elements from one embodiment may be added to anotherembodiment. For example, orders of processes described herein may bechanged and are not limited to the manner described herein. Moreover,the actions any flow diagram need not be implemented in the order shown;nor do all of the acts necessarily need to be performed. Also, thoseacts that are not dependent on other acts may be performed in parallelwith the other acts. The scope of the present invention, however, is byno means limited by these specific examples. Numerous variations,whether explicitly given in the specification or not, such asdifferences in structure, dimension, and use of material, are possible.The scope of the invention is at least as broad as given by thefollowing claims.

1. A method comprising: identifying a socket associated with a virtualoperating system migration to a destination computer; assigning at leastone buffer to store a portion of a network protocol unit carryinginformation associated with the virtual operating system migration;selectively transferring a received network protocol unit carryinginformation associated with the virtual operating system migration tothe assigned buffer in response the sequence number of the receivednetwork protocol unit matching an expected sequence number and thereceived network protocol unit being within the socket; and selectivelyproviding availability of a payload of the received network protocolunit directly from the assigned buffer.
 2. The method of claim 1,wherein the identifying comprises establishing the socket with atransmitter of network protocol units involved in the virtual operatingsystem migration to the destination computer.
 3. The method of claim 1,wherein the assigning comprises assigning a header buffer and a payloadbuffer.
 4. The method of claim 3, wherein contents of the payload bufferare available to application logic independent of copying of thecontents from the payload buffer to another buffer.
 5. The method ofclaim 3, further comprising validating protocol compliance of a headerstored in the header buffer.
 6. The method of claim 1, wherein theassigning comprises transferring identification of the at least onebuffer to a network component.
 7. The method of claim 1, wherein thereceived network protocol unit carrying information associated with thevirtual operating system migration complies with the TCP/IPspecification.
 8. The method of claim 1, further comprising assigning asecond buffer for a portion of a network protocol unit that is notassociated with the virtual operating system migration.
 9. The method ofclaim 8, further comprising selectively transferring the receivednetwork protocol unit to the assigned second buffer in response thesequence number of the received network protocol unit not matching anexpected sequence number.
 10. The method of claim 8, further comprisingselectively transferring the received network protocol unit to theassigned second buffer in response to the received network protocol unitnot being within the socket.
 11. A computer readable storage mediumstoring instructions thereon that when executed by a computer cause thecomputer to: determine a socket associated with an operating systemmigration to a destination computer; provide at least one bufferassignment to store a portion of a network protocol unit carryinginformation associated with the operating system migration; andselectively request transfer of a received network protocol unitcarrying information associated with the operating system migration tothe assigned buffer in response to the sequence number of the receivednetwork protocol unit matching an expected sequence number and thereceived network protocol unit being within the socket.
 12. The mediumof claim 11, wherein the instructions to determine comprise instructionsto establish the socket with a transmitter of the operating system. 13.The medium of claim 11, wherein the instructions to provide compriseinstructions to assign a header buffer and a payload buffer.
 14. Themedium of claim 13, wherein contents of the payload buffer are availableto an application independent of copying of the contents from thepayload buffer to another buffer.
 15. The medium of claim 11, whereinthe received network protocol unit carrying information associated withthe operating system migration complies with the TCP/IP specification.16. The medium of claim 11, further comprising instructions to assign asecond buffer for a portion of a network protocol unit that is notassociated with the operating system migration operation.
 17. The mediumof claim 16, further comprising instructions to selectively transfer thereceived network protocol unit to the assigned second buffer in responsethe sequence number of the received network protocol unit not matchingan expected sequence number.
 18. The medium of claim 16, furthercomprising instructions to selectively transfer the received networkprotocol unit to the assigned second buffer in response to the receivednetwork protocol unit not being within the socket.
 19. A systemcomprising: a host system comprising a first buffer, second buffer, anda data mover logic; a network component communicatively coupled to thehost system, the network component comprising: logic to receive a socketassociated with a virtual operating system migration to the host system,logic to receive at least one buffer assignment to store a portion of anetwork protocol unit carrying information associated with the virtualoperating system migration, and logic to selectively transfer a receivednetwork protocol unit carrying information associated with the virtualoperating system migration to the assigned buffer in response to thesequence number of the received network protocol unit matching anexpected sequence number and the received network protocol unit beingwithin the socket; and a network medium communicatively coupled to thenetwork component.
 20. The system of claim 19, further comprising a busto communicatively couple the host system and the network component. 21.The system of claim 19, wherein at least one the buffer assignmentcomprises an assignment of a header buffer and a payload buffer.
 22. Thesystem of claim 21, wherein contents of the payload buffer are availableto an application independent of copying of the contents from thepayload buffer to another buffer.